The invention relates to a temperature responsive switch, and more particularly, to a temperature responsive switch which may be used to control the temperature responses of automobiles, for example, the recirculation of exhaust gas, or ignition timing in accordance with the temperature of an engine.
For on-board purification of an exhaust gas of an automobile, the recirculation of an exhaust gas or an ignition timing is controlled in accordance with the temperature of an engine or of an exhaust gas. In such control, the engine temperature or the temperature of the exhaust gas is detected by a temperature responsive switch. In these applications, a temperature responsive switch includes a bimetal as a temperature responsive element which becomes deformed to open or close switch contacts in accordance with the temperature which the bimetal assumes. Accordingly, an on-off operation may be achieved as by closing or opening the contacts below and above a given temperature, for example.
Since the control of the recirculation of the exhaust gas or the ignition timing increases the exhaust gas processing efficiency, the recent trend is from an on-off control (two-value control) to a multi-value control. In a multi-value control, the temperature range of the engine or the exhaust gas is divided into at least three regions of low, medium and high temperatures, in each of which a separate processing of the exhaust gas or a separate control of the ignition timing is made. Accordingly, at least two temperature responsive switches having different switching points are utilized in a multi-value control. As a result of the requirements imposed on such temperature responsive switches, including the resistance to high temperatures and to shocks, the switch is formed as a rigid structure, resulting in a bulky construction. Hence, the provision of two or more temperature responsive switches on a vehicle results in an increased space requirement and an increased assembling operation.